House fly (Musca domestica): a review of control strategies for a challenging pest

Musca domestica L. (Diptera: Muscidae), commonly called the house fly, is a major domestic, medical and veterinary pest that causes irritation, spoils food and acts as a vector for many pathogenic organisms. In this paper, the social and health problems related to housefly are introduced with the associated need to control its population. Physical and chemical methods of house fly control are briefly discussed. The main focus of this review is on the biological control methods for house fly control, that comprise botanical, fungal, bacterial and parasitoid agents. Although several biocontrol agents are still in the nascent stage, some of them (especially fungal and parasitoid agents) have shown reliable field performance and seem to be suitable candidates for commercialization. However, the majority of these laboratory and field studies have been conducted in the temperate region. It remains to be seen whether the application of biocontrol agents would be feasible in tropical environments. The integrated pest management practices, which can provide more reliable field performance, have also been discussed. A multi-dimensional approach that exerts control on all the life stages of house fly, but simultaneously preserves the fly's natural enemies could be an ecologically sustainable way of maintaining the fly populations below maximally acceptable limits.     

Identification and comprehensive evaluation of a novel biocontrol agent Bacillus atrophaeus JZB120050

Abstract

Bacillus spp. have long been used as biocontrol agents because of their efficient broad-spectrum antimicrobial activity. We identified a novel strain of Bacillus atrophaeus, named JZB120050, from soil. B. atrophaeus JZB120050 had a strong inhibitory effect against Botrytis cinerea and many other phytopathogens. Gas chromatography-mass spectrometry showed that B. atrophaeus JZB120050 produced many secondary metabolites, such as alkanes, alkenes and acids; some of which were related to pathogen inhibition. Enzyme activity analysis showed that B. atrophaeus JZB120050 secreted cell-wall-degrading enzymes, including chitinase, glucanase and protease, which degraded fungal cell walls. Both the novel glucanase gene bglu and chitinase gene chit1 were cloned and heterologously expressed in Escherichia coli and the products showed strong enzyme activity. In addition, B. atrophaeus JZB120050 secreted siderophores and formed a significant biofilm. Future studies should focus on these antimicrobial factors to facilitate widespread application in the field of agricultural biocontrol.     

Effect of in vitro administered 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on DNA-binding activities of nuclear transcription factors in NIH-3T3 mouse fibroblasts

Abstract

Most modern pesticides are expensive. Application of excessive dosage rates is likely to cause undesirable biological side‐effects and is economically wasteful. Non‐uniform distribution of the spray cloud, or application at the wrong time, may result in failure to control the pest. It is the responsibility of the field operator to acquire sufficient knowledge and skill to ensure proper use of the control agents, to increase efficiency of their usage and to reduce unwanted side‐effects. To achieve this goal, he must take into consideration the various physical factors that govern field performance of pesticides.

A simple relationship exists between the spray volume and emission rate used, and droplet size produced. The use of extremely low spray volumes (i.e., those less than 2.0 litre per ha) for forest insect control in Canada, as opposed to higher volumes used in agriculture, necessitates the release of fine droplets (ranging from 20 to 70 μm in diameter) to obtain adequate coverage of the target area. These droplets take a long time to sediment downwards, evaporate in‐flight, become smaller in size and/or form powdery residues, thus contributing to off‐target drift and impaired droplet adhesion to target surfaces. Physical factors such as rain washing, degradation by sunlight and erosion by wind also influence the longevity of pesticide deposits on foliage which is crucial during the critical period of pest control.

Factors affecting the mode of entry into insects are related to the type of ingredients used in formulation. If a pesticide acts via crawling contact, formulations which would provide surface deposits would be more beneficial than emulsions or oil‐based mixes which tend to undergo penetration into foliar cuticle. Physical factors that affect field performance of a pesticide tank mix are related to phase separation and ‘breakdown of emulsions’ in the application equipment; ‘agglomeration and caking’ of wettable powder dispersions at the bottom of the tank; impaired flow behaviour of highly viscous formulations; and coarse atomization of high‐viscosity tank mixes leading to poor target cover.     

Preliminary evaluation of insecticide resistance in a strain of Musca domestica (Diptera: Muscidae) from an intensive chicken farm of Northern Italy

The house fly, Musca domestica L., a relevant sanitary pest, is mainly controlled by insecticides. However, an inappropriate use of chemicals may induce resistance, treatment efficacy decline and environmental damages. We evaluated toxicity of some organophosphates, pyrethroids, spinosad and neonicotinoids by topical applications on adults of a M. domestica strain (OcRo) collected from an intensive chicken farm in Northern Italy, in comparison to a susceptible strain (s-DBF). The OcRo strain exhibited higher levels of resistance (RR??) to four pesticides in comparison to s-DBF. Spinosad and imidacloprid had very low RR??, thus were still efficient in OcRo control. We also tested resistance to pesticides in OcRo after topical applications of synergistic compounds. Hydrolases were involved in phosphorganic detoxification and cytochrome P450 monoxygenases in that of pyrethroids. These results indicate that OcRo strain is now multiresistant to organophosphates and pyrethroids, and this should be considered for an environmentally safe pest management.     

Assessment of susceptibility of olive cultivars to the Bactrocera oleae (Gmelin, 1790) and Camarosporium dalmaticum (Thüm.) Zachos & Tzav.-Klon. attacks in Calabria (Southern Italy)

Within the framework of research concerning the application of techniques alternative to chemical pesticides for control of parasites, the C.R.A. Experimental Institute for Olive Growing for many years has been performing a large investigation in order to detect sources of genetic resistance in olive germplasm. In the present study we observed the behavior related to the olive fly (Bactrocera oleae) infestation and Camarosporium dalmaticum infection of ten olive cultivars farmed under the same agronomic and climatic conditions in Calabria, Southern Italy. The sampling and the data collecting were carried out in three different ripening times.The drupe amount of oleuropein and cyanidine was detected by laboratory analyses in order to verify a possible correlation between these molecules and the level of infestation/infection of the above-mentioned parasites. The obtained data were submitted to analysis of variance. In relation to the fungal infection the results displayed that cvs Tonda nera dolce showed the lowest susceptibility, while the cv Giarraffa turned out to be the most susceptible. The less susceptible cultivars to the phytophagous were Tonda nera dolce and Bhardi Tirana. Since the less susceptible cultivar to olive fly attacks are the same observed in relation to the susceptibility to olive fruit rot, it is suggested a relation between the olive fly infestation and the fungal infection. It suggests the utility to achieve these results both to transfer directly to the farmers' world and to emphasize ecosystem health and biodiversity conservation.     

Dose-response relationship in lethal and behavioural effects of different insecticides on the parasitic wasp Aphidius ervi

Neurotoxic insecticides are widely used for crop protection and behavioural perturbations can be expected in surviving beneficial insects, including parasitoids of pest insects. The present study aims to investigate the relationship between the dose of insecticide parasitoids have been exposed to, and the subsequent ability of these parasitoids to respond to host-related cues. A four-armed olfactometer, a design widely used to observe orientation responses in various insects and parasitoids in particular, was chosen to investigate the dose-response relationship. The species studied was Aphidius ervi, a relatively generalist parasitoid of aphids, and commercialised for biological control and integrated pest management. Active ingredients with similar and different modes of action on the nervous system were compared: a pyrethroid (lambda-cyhalothrin), an organophosphate (chlorpyrifos), a carbamate (pirimicarb) and a carbamyltriazole (triazamate). Adult females were exposed to dry residues on glass for 24 h. LD50 were calculated and predicted a high risk of mortality at the field application rate. The effect of five increasing residual doses of each active ingredient was tested on responses to plant-host odour in the olfactometer, from sublethal doses to LD50, and up to LD70 for some products. It appeared that none of the doses of lambda-cyhalothrin, chlorpyriphos and pirimicarb had any effect on A. ervi responses to the odour from the aphid-infested plant (Myzus persicae on oilseed rape). But for triazamate, a significant dose-behavioural response was quantified and attraction to the odour was no longer significant in females surviving the LD50. The possible explanations for the presence or absence of effect, depending on the insecticide are discussed.     

A multi-step bioassay to assess the effect of the deltamethrin on the parasitic wasp Aphidius ervi

Insecticides are widely used for crop protection. Effectiveness of pesticides and beneficial arthropods in an Integrated Pest Management (IPM) program requires a full understanding of how specific pesticides alter natural enemy effectiveness. This may require evaluation of chemicals at different life stages of the insect considered, on different physiological and behavioural components, and also on population dynamic components such as recolonization capacities after a pesticide treatment. Aphidius ervi Haliday (Hymenoptera: Braconidae) is an aphid parasitoid commonly used for the biological control of aphid populations. In this work, our aim was to assess the effects of deltamethrin (pyrethroid) treatments on this parasitoid using a multi-step bioassay. We evaluated its effects on parasitoid emergence, adult survival and longevity, and host searching. Two exposure methods were used, topical and spray, to evaluate impact of the deltamethrin field rate (6.25ga.i./ha) and also to compare the methods of exposure. A four-armed olfactometer was used to investigate effect of deltamethrin on host searching behaviour. When applied at the rate of field exposure, deltamethrin reduced the adult longevity but not the rate of emergence from mummies. Effects varied between the two exposure methods. Two indices were defined: the "population survival index" to measure capacity of parasitoids to recolonize a treated field and the "reproductive potential" to estimate the reduction in reproduction as a function of longevity decrease. These indices predicted effects of deltamethrin on A. ervi in terms of mortality and reduction of recolonization capacities. However, adults that survived residual exposure to deltamethrin retained their ability to orient to host odours. The implications of results in IPM and interest of the methodology used are both discussed.     

Host location behavior of Cotesia plutellae Kurdjumov (Hymenoptera: Braconidae) in ambient and moderately elevated ozone in field conditions

In field O₃-enrichment experiments increased herbivore densities have been reported, which could be due to negatively affected host location behavior of natural enemies. We addressed the impact of doubling background O₃ on the host location of the parasitoid Cotesia plutellae by conducting 24-h trials in an open-air O₃-fumigation system during two consecutive years. Two circles (radii 1.40 and 4.00 m) of Plutella xylostella-infested potted cabbage plants were placed in the O₃ and ambient plots. Female wasps were released into each plot from the center, and observed 5 times over a 24-h period to assess their host location capability. Thereafter, plants were kept in laboratory conditions until larvae pupation to determine parasitism rates. No significant differences were detected between ambient and O₃-enriched environments either in the number of wasps found in the field, or in the percentages of parasitized larvae. This suggests that moderately elevated O₃ will not affect the behavior of this parasitoid.     

Fungal levels in houses in the Fukushima Daiichi Nuclear Power Plant evacuation zone after the Great East Japan Earthquake

Residences located within 20 km of the damaged Fukushima Daiichi Nuclear Power Plant were evacuated shortly after the Great East Japan Earthquake. The levels of airborne and surface fungi were measured in six houses in the evacuation zone in August 2012 and February 2013. Airborne fungal levels in all of the houses in the summer were higher than the environmental standard levels for residential houses published in Architectural Institute of Japan (>1000 colony-forming units [CFU]/m³). In two houses whose residents rarely returned to visit, fungal levels were extremely high (>52,000 CFU/m³). Although fungal levels in the winter were much lower than those in the summer, they were still higher than environmental standard levels in several houses. Indoor fungal levels were significantly inversely related to the frequency with which residents returned, but they were not correlated with the air exchange rates, temperature, humidity, or radiation levels. Cladosporium spp. and Penicillium spp. were detected in every house. Aspergillus section Circumdati (Aspergillus ochraceus group) was also detected in several houses. These fungi produced ochratoxin A and ochratoxin B, which have nephrotoxic and carcinogenic potential. The present study suggests that further monitoring of fungal levels is necessary in houses in the Fukushima Daiichi Nuclear Power Plant evacuation zone, and that some houses may require fungal disinfection.

Implications: The results suggest that residents’ health could be at risk owing to the high levels of airborne fungi and toxic fungi Aspergillus section Circumdati. Therefore, monitoring and decontamination/disinfection of fungi are strongly recommended before residents are allowed to return permanently to their homes. In addition, returning to home with a certain frequency and adequate ventilation are necessary during similar situations, e.g., when residents cannot stay in their homes for a long period, because fungal levels in houses in the Fukushima Daiichi Nuclear Power Plant evacuation zone were inversely correlated with the frequency with which residents returned to visit their houses.     

Lethal and sublethal effects of four essential oils on the egg parasitoids Trissolcus basalis

The essential oils from leaves of Schinus molle var. areira, Aloysia citriodora, Origanum vulgare and Thymus vulgaris have showed potential as phytoinsecticides against the green stink bug, Nezara viridula. In this work were evaluated their toxicological and behavioral effects on the parasitoid Trissolcus basalis, a biological control agent of this pest insect. Essential oils were obtained via hydrodestillation from fresh leaves. Insecticide activity in T. basalis females was evaluated in direct contact and fumigation bioassays. Behavioral effects were evaluated in olfactometer bioassays. To evaluate the residual toxicity, females of the parasitoids were exposed to oil residues; in these insects, the sublethal effects were evaluated (potential parasitism and survivorship of immature stages). The essential oils from O. vulgare and T. vulgaris proved to be highly selective when used as fumigant and did not change parasitoid behavior. After one week, the residues of these oils were harmless and did not show sublethal effects against T. basalis. According with these results, essential oils have potential applications for the integrated management of N. viridula.     

Insecticidal activity of raw ethanolic extracts from Magnolia dealbata Zucc on a tephritid pest

Ethanolic extracts from Magnolia dealbata (Zucc.) (Magnoliaceae); leaves, bark, seeds, sarcotesta and flowers were evaluated for insecticidal activity against adults of the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae). Using feeding bioassays composed from sugar-extract mixtures, only the extract from sarcotesta indicated insecticidal activity against the flies. The extracts from the other four plant tissues (leaves, bark, seeds and flowers) did not manifest any biological activity. The most effective extract was obtained from oven-dried sarcotesta, whereas extracts from fresh sarcotesta were inactive. Our results suggest that M. dealbata sarcotesta contains secondary metabolites with insecticidal activity against A. ludens adults. These metabolites are as potent as natural pyrethins and represent a potential substance for controlling this type of pest.     

Effect of air-conditioner on fungal contamination

Air-conditioners (AC) produce much dew and wet conditions inside their apparatus, when in operation. We studied the fungal contamination in AC and found that the average fungal contamination of AC filters was about 5-fold greater than that of a carpet, and Cladosporium and Penicillium were predominant in AC filters. The fungal contamination inside AC, which were used everyday, increased more markedly than those not used daily, e.g. a few days per week or rarely. Moreover, the airborne fungal contamination in rooms during air-conditioning was about 2-fold greater than one in rooms without AC, and was highest when air-conditioning started and decreased gradually with time. We recognized that the airborne fungal contamination was controlled by the environmental condition of the rooms, in which AC were used. It is suggested that AC might promote mold allergies in users via airborne fungal spores derived from the AC. On the other hand, AC was estimated to remove moisture in the room atmosphere and carpets, and reduce the relative humidity in rooms. It was found that the average fungal contamination in the house dust of carpets with AC was suppressed by two-third of that in rooms without AC. The use of AC for suppressing fungal hazards was discussed.     

Effect of gaseous chlorine dioxide on indoor microbial contaminants

Traditional and modern techniques for bioaerosol enumeration were used to evaluate the relative efficiency of gaseous chlorine dioxide (ClO2) in reducing the indoor microbial contamination under field and laboratory conditions. The field study was performed in a highly microbially contaminated house, which had had an undetected roof leak for an extended period of time and exhibited large areas of visible microbial growth. Air concentrations of culturable fungi and bacteria, total fungi determined by microscopic count and polymerase chain reaction (PCR) assays, endotoxin, and (1 --> 3)-beta-D-glucan were determined before and after the house was tented and treated with ClO2. The laboratory study was designed to evaluate the efficiency of ClO2 treatment against known concentrations of spores of Aspergillus versicolor and Stachybotrys chartarum on filter paper (surrogate for surface treatment). These species are commonly found in damp indoor environments and were detected in the field study. Upon analysis of the environmental data from the treated house, it was found that the culturable bacteria and fungi as well as total count of fungi (as determined by microscopic count and PCR) were decreased at least 85% after the ClO2 application. However, microscopic analyses of tape samples collected from surfaces after treatment showed that the fungal structures were still present on surfaces. There was no statistically significant change in airborne endotoxin and (1 --> 3)-beta-D-glucan concentration in the field study. The laboratory study supported these results and showed a nonsignificant increase in the concentration of (1 --> 3)-beta-D-glucan after ClO2 treatment.     

Indoor- and outdoor-derived contaminants in urban and rural homes in Ottawa, Ontario, Canada

Indoor and outdoor air contaminants have largely been treated separately in studies of their respective effects on respiratory and nonrespiratory health. In this paper, we report the results of a comprehensive study of key contaminants in 10 urban and 10 rural homes in Ottawa, Ontario, Canada. The analyses included house dust mite and cat allergens along with the fungal inflammatory polysaccharide beta1,3-D-glucan in settled dust and fine particulate matter, coarse particulate matter, ergosterol, glucan, and endotoxin from air samples. In addition, black carbon was continuously measured for 7 days. A detailed physical assessment of the house and patterns of use were undertaken, including a careful inspection for mold and water damage, as well as measurements of air leakage. The performance of the houses and the range and distribution of the contaminants measured were largely similar to that of previous Canadian studies. For certain combinations, it is thought that the presence of both allergen and inflammatory materials increases asthma symptoms. House-by-house comparisons of airborne concentrations of inflammatory compounds measured (endotoxin, fine particulate matter, and fungal glucan) with dust mite allergens indicated that certain houses had relatively higher amounts of both kinds of materials.     

Efficacy of new mass-trapping devices against Bactrocera oleae (Diptera tephritidae) for minimizing pesticide input in agroecosystems

Decreasing pesticide use in olive groves is central to controlling pathogens and pests such as Bactrocera oleae. This has led to the development of mass trapping devices which not only minimize pesticide use but, with improved efficacy of attractants, also decrease costs associated with pest control and ensures that the quality of olive oil is safe for human consumption. This study was undertaken to test a new device which utilizes reduced quantities of both insecticide (lambda-cyalothrin) as well as the female olive fly pheromone (1,7-dioxaspiro-(5.5)-undecane). The new device was tested against an older device manufactured by the same company. The use of plastic polymers as substrate for encapsulating the pheromone allowed for a slower pheromone release, prolonging the efficacy and duration and thus reducing costs. The density of adult populations was monitored using yellow chromotropic traps that were checked every ten days and the degree of olive infestation, as determined by preimago stages, was assessed by analyzing 100 drupes per plot. Infestation analyses were performed every ten days. The control plot had the lowest density of adults and the highest drupe infestation rate. The new devices were more effective than the older devices in both attracting adults and controlling infestation of drupes. Moreover, the new devices containing reduced amounts of pheromone and insecticide were cheaper and exhibited longer functional efficacy. In addition to the slower release of attractants, the plastic polymers used in these newer devices were also more resistant to mechanical and weather degradations. Results demonstrate that mass trapping can indeed be an effective means of controlling B. oleae via eco-sustainable olive farming.     

Assessment of susceptibility of olive cultivars to the Bactrocera oleae (Gmelin, 1790) and Camarosporium dalmaticum (Thüm.) Zachos & Tzav.-Klon. attacks in Calabria (Southern Italy)

Within the framework of research concerning the application of techniques alternative to chemical pesticides for control of parasites, the C.R.A. Experimental Institute for Olive Growing for many years has been performing a large investigation in order to detect sources of genetic resistance in olive germplasm. In the present study we observed the behavior related to the olive fly (Bactrocera oleae) infestation and Camarosporium dalmaticum infection of ten olive cultivars farmed under the same agronomic and climatic conditions in Calabria, Southern Italy. The sampling and the data collecting were carried out in three different ripening times.The drupe amount of oleuropein and cyanidine was detected by laboratory analyses in order to verify a possible correlation between these molecules and the level of infestation/infection of the above-mentioned parasites. The obtained data were submitted to analysis of variance. In relation to the fungal infection the results displayed that cvs Tonda nera dolce showed the lowest susceptibility, while the cv Giarraffa turned out to be the most susceptible. The less susceptible cultivars to the phytophagous were Tonda nera dolce and Bhardi Tirana. Since the less susceptible cultivar to olive fly attacks are the same observed in relation to the susceptibility to olive fruit rot, it is suggested a relation between the olive fly infestation and the fungal infection. It suggests the utility to achieve these results both to transfer directly to the farmers' world and to emphasize ecosystem health and biodiversity conservation.     

Evaluation of the impact on entomocoenosis of active agents allowed in organic olive farming against Bactrocera oleae (Gmelin, 1790)

Several attempts for evaluating environmental impact of active agents allowed in organic olive farming against Bactrocera oleae have been made, but very few studies were performed contemporaneously on more than one of them. Insects were chosen as indicators because they are known to react very quickly to environmental perturbations, mainly at the community level. In fact, the coenosis is the functional unit interacting with biotic and abiotic environmental parameters. Seven taxa, known for their sensitivity to habitat alterations, were sampled and grouped in functional groups: predators and parasitoids, phytophagouses and pollinators. The coenotic balance between these two functional groups was analyzed. The study was carried out in an organic olive orchard in the municipality of Terranova da Sibari, Cosenza, Southern Italy. The tested active agents (Azadirachtin, Rotenone, Copper Oxychloride) were sprayed twice (end of September and middle October). During the treatments the population dynamics of all the taxa were knocked-down. No one tested compound seems to be harmless to the entomocoenosis, particularly on phytophagouses and pollinators. In truly organic farming it is necessary to provide natural refuge areas to beneficial insects (i.e. pest antagonists) in which no active agents are sprayed and alternative preys could be found.     

Isolation of culturable mycobiota from agricultural soils and determination of tolerance to glyphosate of nontoxigenic Aspergillus section Flavi strains

Glyphosate-based herbicides are extensively used in Argentina's agricultural system to control undesirable weeds. This study was conducted to evaluate the culturable mycobiota [colony forming units (CFU) g^?1 and frequency of fungal genera or species] from an agricultural field exposed to pesticides. In addition, we evaluated the tolerance of A. oryzae and nontoxigenic A. flavus strains to high concentrations (100 to 500 mM – 17,000 to 84,500 ppm) of a glyphosate commercial formulation. The analysis of the mycobiota showed that the frequency of the main fungal genera varied according to the analyzed sampling period. Aspergillus spp. or Aspergillus section Flavi strains were isolated from 20 to 100% of the soil samples. Sterilia spp. were also observed throughout the sampling (50 to 100%). Aspergillus section Flavi tolerance assays showed that all of the tested strains were able to develop at the highest glyphosate concentration tested regardless of the water availability conditions. In general, significant reductions in growth rates were observed with increasing concentrations of the herbicide. However, a complete inhibition of fungal growth was not observed with the concentrations assayed. This study contributes to the knowledge of culturable mycobiota from agricultural soils exposed to pesticides and provides evidence on the effective growth ability of A. oryzae and nontoxigenic A. flavus strains exposed to high glyphosate concentrations in vitro.     

Structural changes in soil communities after triclopyr application in soils invaded by Acacia dealbata Link

Triclopyr is a commonly used herbicide in the control of woody plants and can exhibit toxic effects to soil microorganisms. However, the impact on soils invaded by plant exotics has not yet been addressed. Here, we present the results of an 18-month field study conducted to evaluate the impact of triclopyr on the structure of fungal and bacterial communities in soils invaded by Acacia dealbata Link, through the use of denature gradient gel electrophoresis. After triclopyr application, analyses of bacterial fingerprints suggested a change in the structure of the soil bacterial community, whereas the structure of the soil fungal community remained unaltered. Bacterial density and F:B ratio values changed across the year but were not altered due to herbicide spraying. On the contrary, fungal diversity was increased in plots sprayed with triclopyr 5 months after the first application. Richness and diversity (H´) of both bacteria and fungi were not modified after triclopyr application.     

Conditioning of Fly Ash with Ammonia

This paper presents the results of an investigation of the conditioning of fly ash with ammonia in electrostatic pre-cipitators of power plants operated by the Tennessee Valley Authority. It focuses attention primarily on the mechanisms of conditioning encountered under the particular circumstances available for study. No effect of ammonia on the electrical resistivity of fly ash was evident. Instead, the effect of ammonia appeared to be an enhancement pf the space-charge component of the electric field used for charging and precipitating particles of fly ash. In addition, a second effect appeared to be an increase in the cohesiveness of precipitated ash and a reduction in the quantity of ash reentrained during electrode rapping. Data demonstrating the value of ammonia conditioning for lowering the emission pf fly ash during three precipitator studies are presented. Reasons for the ineffectiveness of ammonia conditioning during a fourth precipitator study are discussed. In conclusion, comments are made about the effects to be expected from ammonia conditioning under circumr stances different from those investigated experimentally, particularly with ammonia as a conditioning agent for fly ash from low sulfur western coal.